I think Golden State would be the greatest team of all-time if they had Harden. Harden would be unstoppable with that supporting cast. Steph would struggle to be the focal point at all times IMO. His teammates really take a lot of pressure off of him.
Harden running the point for GS would be so sick. Klay would obviously have to guard PGs. GS's defense would probably suffer as a result, but that offense would be unbelievable. I do think Harden makes that offense better as hard to believe as that is. It would be hilarious watching teams try to guard Harden with him playing next to a guy like Thompson every night.
I honestly think Harden is better suited for the way the Rockets play and Curry better suited for the way the Warriors play.
If Harden had the point guard equivalent of Klay Thompson (Good defender and a real three point shooter), the Rockets would be competing with the Warriors for the best record in the NBA. If Beverley was the Beverley from last year, we would be competing with the Warriors for the best record.
Honestly, I think both teams would be worse. A backcourt of Beverley and Curry wouldn't work very well. Neither would a backcourt of Harden and Thompson. Too much overlap in both cases and in both cases the team has been trying to build around Harden and build around Curry. They have different skills, and if you removed one and plugged it into a system that was built for the other, I don't think it would work. That said, I think Harden is more important to the Rockets and I think the Rockets with Curry would be 'more worse' than the Warriors with Harden.
Curry is a much better distributor and shooter - I love Harden but Curry is just a little bit better, IMO. DD